(1) Field of the Invention
The present invention relates to an ink jet head, and more particularly to an ink jet head including a current limiter for limiting a current flowing through ink when purging.
(2) Description of the Related Art
Japanese Patent Publication (Kokai) No. 2002-79666 discloses a conventional ink jet head 2a as is shown in FIG. 10. FIG. 10 is a cross section of a main portion of ink jet head 2a. A nozzle plate 4 is fixed to a tip of ink jet head 2a. A plurality of nozzles 5 are formed in nozzle plate 4 in a line such that each nozzle corresponds to a respective ink chamber 6. When current from a power supply flows through an electrode 10 disposed on an actuator 9 forming a part of ink chamber 6, actuator 9 deforms. Thus, ink is ejected from nozzle 5. A plate 7 having an opening is attached to nozzle plate 4 overlapping with nozzle 5 such that the ejected ink from nozzle 5 passes through the opening. Plate 7 prevents the tip of ink jet head 2a from being contaminated by ink seeping from nozzles 5.
If plate 7 is electrically ungrounded, friction between the surface of plate 7 and either a transferred recording paper or the flow of dried air produces static electricity on plate 7. The static electricity causes a discharge current to momentarily flow through a conductive member in ink jet head 2a and an integrated circuit (IC) for driving ink jet head 2a. If the discharge current is big, the IC may break down. To prevent such a breakdown, plate 7 is electrically grounded to have no charge thereon, using a conductive material therefore, e.g., stainless steel, nickel, aluminum, and so on.
Conventionally, an operation for purging ink, so called “purge”, is also performed frequently to remove contaminants adjacent to the nozzles, e.g., ink having increased viscosity, bulky particles, and so on, thereby keeping ink ejection from the ink jet head stable. During purging, ink pressure generated in an ink chamber by an energized actuator causes ink to be forcibly pushed out or flushed out from the nozzles to remove the contaminants while the ink jet head is at rest and not in a printing operation.
Inventors of the present invention found that temperature of integrated circuit (IC) for driving the ink jet head goes extraordinarily high when the purge is repeated, thereby bringing about deterioration or breakdown of the IC.